1. Field of the Invention
The present invention relates to an ink jet ink for use together with a pigmented ink. Particularly, the present invention relates to an ink jet ink which is excellent in the bleeding resistance and can suppress the occurrence of the metallic luster, the so-called bronzing phenomenon, when images are formed on a recording medium. Further, the present invention relates to an ink jet recording method, an ink cartridge, an ink set and an image forming method which are provided by use of the ink jet ink.
2. Description of the Related Art
As a coloring material of an ink jet ink having a hue of cyan, dyes having a phthalocyanine skeleton are broadly used because they are excellent in light resistance, have a high fastness against humidity and temperature, and are good in color developability.
However, problems with phthalocyanine dyes include the easy occurrence of the metallic luster, the so-called bronzing phenomenon, due to high aggregation properties of the dyes. When the bronzing phenomenon occurs on a recorded matter, the optical reflection characteristics change and the color developability and hue of images remarkably change, causing a remarkable decrease in image quality. As methods for improving the bronzing resistance, the following methods are known. For example, the addition of an alkanolamine such as N-hydroxyethylmorpholine, monoethanolamine, diethanolamine or triethanolamine to an ink, and the improvement in the permeability of an ink into a recording medium, are known. The addition of a basic amino acid to an ink is also known (for example, see Japanese Patent Application Laid-Open No. H07-228810).
The phthalocyanine dyes further have a tendency of being inferior in the fastness against environmental gases in the air (ozone, NOx, SO2), especially ozone gas. Particularly, the low fastness in a recorded matter recorded on a recording medium having an ink receiving layer including an inorganic substance such as alumina or silica is outstanding and when the recorded matters are allowed to be left indoor for a long time, the dyes remarkably fade. For improving the ozone resistance, there is a proposal about devising a structure of phthalocyanine dyes (for example, see Japanese Patent No. 2942319, WO 2004/087815 Pamphlet and Japanese Patent Application Laid-Open No. 2004-323605).
On the other hand, on a recording medium, for making full-color images including adjacent regions different in color from each other to be of high quality, there is a problem of effectively suppressing the bleeding (color mixing) on boundaries between the regions of each color, especially boundaries between color images and black images. For improving the bleeding resistance, various attempts have been made. For example, the addition of a polyvalent metal to a color ink in which a dye is used as a coloring material, is known (for example, see Japanese Patent Application Laid-Open No. H06-106841). A method of suppressing the bleeding by aggregating a coloring material (pigment) of an adjacently recorded black ink by adjusting the pH of the color ink to an acid range, is known (for example, see Japanese Patent Application Laid-Open No. H05-208548).
Additionally, higher image-quality has been accomplished in recent years as represented by minimization of ink drops. Hence, inks are required to have much stricter characteristics on reliabilities of clogging and ejection stability of a recording head.